Liquid fuel supply systems for internal combustion engines



Dec. 2, 1969 J. c. P. THORNBER LIQUID FUEL SUPPLY SYSTEMS FOR INTERNAL COMBUSTION ENGINES Filed Oct. 31, 1967 w/nmui- Ni mm mm am m Ill-I'll MVAM ATTORNEYS United States Patent 3,481,315 LIQUID FUEL SUPPLY SYSTEMS FOR INTERNAL COMBUSTION ENGINES John Charles Powell Thornber, London, England, assignor to C.A.V. Limited, Acton, London, England, a British company Filed Oct. 31, 1967, Ser. No. 679,433 Claims priority, application Great Britain, Nov. 11, 1966, 50,654/ 66 Int. Cl. F02b 3/00; F02m 47/02 U.C. Cl. 12332 7 Claims ABSTRACT OF THE DISCLOSURE In the complete specification of British patent No. 1,060,181 there is described a liquid fuel supply system for internal combustion engines and of the kind including an injection nozzle which is mounted in the body of the engine and through which fuel can be delivered to a combustion space of the engine and a fuel pump for supplying fuel to the nozzle in timed relationship to the engine, said nozzle incorporating a pressure responsive valve for controlling the flow of fuel therethrough, and a device associated with or adjacent to the nozzle, the device comprising in combination a valve member slidable in a cylinder, one end of said cylinder being in communication with the fuel pump and the other end of said cylinder being in communication with the nozzle through a first restriction, resilient means urging the valve member towards said one end of the cylinder, and a by-pass passage arranged to be opened by the valve member when the latter has been moved a predetermined extent against the action of the resilient means, the movement of the member towards said other end of the cylinder serving to displace a predetermined quantity of fuel to the nozzle at a restricted rate, said by-pass passage serving, when opened, to place said one end of the cylinder in communication with a point between said nozzle and said restriction.

The object of the present invention is to provide such a system in an improved form.

According to the invention in a system of the kind specified the restriction is constituted by a variable restriction which forms part of a fiow controller whereby the rate of flow of the predetermined quantity of fuel can be controlled.

In the accompanying drawings:

FIGURE 1 is a sectional side elevation of one example of a device in accordance with the invention, and,

FIGURE 2 is a diagrammatic view showing a modification of the device of FIGURE 1.

Referring to FIGURE 1 of the drawing the device comprises a body which is formed of two parts 10 and 11 which are in screw thread engagement with each other. In the part 11 is defined a cylindrical bore 12 the inner end of which is in communication with an outlet passage 13. In use, the outlet passage 13 is in communication with the inlet of a fuel injection nozzle 8. The fuel injection nozzle is of the kind which includes a resiliently loadedvalve member for controlling the flow of fuel through an orifice. The outer end of the bore 12 opens into 3,481,315 Patented Dec. 2, 1969 a chamber which is defined in the part 10 and slidably mounted within the bore is a valve element 14 a portion of which including a head 15, is accommodated in the chamber. In use, the chamber is connected by way of an inlet passage 16 formed in the part 10, with the outlet of a fuel injection pump 9. Moreover, the valve element 14 is loaded by means of a coiled compression spring 17 such that an annular portion of the head 15 bears against the end portion of the part 11 to define a fluid seal therebetween. Moreover, the valve element has formed in its periphery a longitudinal groove or grooves 18 through which, when the element is moved against the action of the spring 17, fuel can flow from the outlet passage 13 to the inlet passage 16.

Within the valve element is a cylinder defined by a bore 19 and formed within the wall of the valve element are three axially spaced ports 20, 21 and 22 and these extend from the cylinder to the groove 18.

Located within the cylinder is a valve element 23 which is loaded by a coiled compression spring 24 into contact with a stop 25 carried by the head 15 of the valve element. When the valve member is in contact with the stop and as shown in the drawing, the ports 20' and 21 are closed. Formed in the end wall of the valve member is an orifice 31. Moreover, the valve member incorporates a bore which accommodates the spring 24 and formed in the wall of the valve member is a port which places the aforesaid bore in communication with a circumferential groove 32 formed in the periphery of the valve member. As shown, when the valve member is against the stop 25 the groove 32 lies substantially midway between the ports 20 and 21 and is out of communication therewith.

Also slidably mounted within the cylinder is a further valve member 33 and this is loaded by a coiled compression spring 34 into contact with a stop 35. In this position and as shown in the drawing, the rear edge of the valve member partially covers the port 22 in order to define a variable restricted orifice. Moreover, the portions of the cylinder on opposite sides of the valve member are in communication by way of an orifice 36 formed in the further valve member. It should be noted that the end of the cylinder adjacent the outlet passage 13 is closed by a plug 37 which also acts as an abutment for the spring 34.

In use, fuel flowing from the fuel injection pump passes by way of the inlet passage 16 into the chamber which accommodates the head 15. The fuel pressure acts upon the end of the valve member 23 and moves the latter against the action of its spring 24. In so doing fuel is displaced through the orifice 36 and the restricted orifice defined by the port 22 and the further valve member 33. The valve member 33 moves against the action of the spring 34 in response to the pressure drop which occurs across the orifice 36 and movement of the valve member against the action of the spring reduces the size of the restricted orifice and consequently the flow rate of fuel to the engine by way of the port 22, the groove 18 and the outlet passage 13 is restricted. The further valve member 33, the port 22 and the spring 34 form the components of a flow controller and by suitable design of each of these components, the flow rate can be varied and can be made to vary in accordance with the pressure of fuel immediately upstream of the orifice 36.

When the valve member 23 has moved such that the port 20 is opened, flow of fuel in the manner described above ceases and the remaining quantity of fuel supplied by the injection pump 9 flows by way of the port 20, the groove 18 and the outlet passage 13. The quantityof fuel which is supplied to the engine at the restricted rate is determined by the movement which the valve member 23 must undertake before the port 20 is opened. When the injection pump ceases to deliver fuel and if it is of the type in which relieving of the pressure in the pipe lines connecting the injection pump and the injection nozzle, takes place after the injection period then the valve element 14 will move against the action of the spring 17 to allow fuel to return towards the injection pump by way of the groove 18 which is now placed in communication directly with the chamber which accommodates the head 15. During this time the valve members move relative to the valve element under the action of their springs respectively. When the return flow of fuel stops the valve element 14 returns to the position in which it is shown in the drawings and the valve members complete their movement relative to the valve element if they have not already done A modification of the above arrangement is shown in FIGURE 2. In this figure the same reference numerals are used where applicable, as are used in FIGURE 1 and the slidable valve element 14 is shown as a spring loaded nonreturn valve. In accordance with the modification the orifice 31 is effectively closed by a plate valve 41. During the initial injection period the plate valve 41 moves with the valve member 23 against the action of a coiled tension spring 42, but it is arranged that as the port 20 is opened by the valve member, the plate valve is prevented by a shoulder 43, from continuing its movement with the valve member. In this manner flow of fuel through the orifice 31 is prevented during the initial injection period.

In both the devices described above the rate of opening of port 20 by the valve member 23 can be controlled by providing a restriction 44 in the port 21. This restriction shown in FIGURE 2. This has the effect of limiting the rate at which fuel can escape from the volume defined between the valve members 23 and 33, thereby it acts to restrict the rate at which the valve member 23 can move during the time when port 20 is being uncovered.

Additional or alternative modification of the rate of opening of port 20 can be obtained by varying the relative axial distance between the ports 20 and 21.

With the arrangements described it is essential to ensure that at the end of the injection stroke of the pump the fuel pressure pertaining within the pipeslines interconnecting the pump 9 and injection nozzles is at a predetermined value at each engine speed and total fuel quantity. In this manner positive and accurate control of the pilot quantity of fuel can be obtained for all speeds of operation irrespective of the total quantity of fuel injected to the engine. Various ways of ensuring that this occurs can be employed and these do not form the subject of the present invention. For example in a conventional in-line pump where each injection pump is complete in itself, each pump may have associated therewith a residual pressure valve which reduces the pressure in the pipe-lines to the predetermined value at the end of the injection stroke. In the case of a distributor type pump where a single injection pump serves a plurality of injection nozzles a special groove associated with a residual pressure valve may be brought into communication with the pipe line at the end of the injection period.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A liquid fuel supply system for an internal combustion engine and including an injection nozzle mounted on the engine and through which fuel can be delivered to a combustion space of the engine, a pressure responsive valve in the nozzle for controlling the flow of fuel therethrough, a fuel pump for supplying fuel to the nozzle in timed relationship with the engine and a device located adjacent the nozzle and through which fuel flows from the pump to the nozzle, said device comprising a cylinder one end of which is in communication with the fuel pump, a valve member slidable in said cylinder, resilient means urging the valve member towards said one end of the cylinder, a flow controller through which the other end of the cylinder is in communication with the nozzle, the valve member being urged against the action of the resilient means to deliver fuel to the engine at a rate which is determined by the flow controller, and a by-pass passage arranged to be opened after a predetermined movement of the valve member against the action of the resilient means, said by-pass passage serving when opened, to place said one end of the cylinder in communication with a point intermediate the flow controller and the nozzle, thereby to allow fuel to flow to the engine at a substantially unrestricted rate.

2. A liquid fuel supply system as claimed in claim 1 in which said fiow controller comprises a further cylinder one end of said further cylinder being in communication with the other end of said cylinder, a further valve member slidable within said further cylinder, resilient means biasing the further valve member in a direction towards said one end of said further cylinder, a restricted flow path through which the opposite ends of the further cylinder are in communication, and a port formed in the wall of said further cylinder, said port being in communication with the nozzle, the port being partially covered by the end of the valve member remote from said one end of the cylinder, the arrangement being such that the effective size of the port which constitutes the variable restriction, is responsive to the pressure drop across said restricted flow path.

3. A liquid fuel supply system as claimed in claim 2 in which said restricted flow path is constituted by a second restriction formed in the further valve member intermediate the ends thereof.

4. A liquid fuel supply system as claimed in claim 3 including a passage formed intermediate the ends of the valve member and a third restriction formed in said passage.

5. A liquid fuel supply system as claimed in claim 4 including a valve for preventing the flow of fuel through said third restriction until the by-pass passage is opened.

6. A liquid fuel supply system as claimed in claim 1 including a further port formed in the wall of said cylinder, a groove formed on the periphery of said valve member, said groove being in communication with the other end of said cylinder and being opened to said second port during movement of the valve member against the action of the resilient means.

7. A liquid fuel supply system as claimed in claim 6 including a fourth restriction in said further port whereby the rate of opening of said by-pass passage can be controlled.

References Cited UNITED STATES PATENTS 3,387,597 6/1968 Wirsching 12332 3,392,715 7/1968 Thoma 123-139 LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R. 239-89 

